The present invention relates to an electrical circuit arrangement having at least two local transmitting units for receiving and coding local measuring signals and for transmitting the coded measuring signals to a central unit, which local transmitting units respectively have a comparator for comparing the local measuring signal with a reference value and triggering means for generating a binary signal to be transmitted to the central unit.
The technical literature discloses a multiplicity of electrical circuit arrangements which are used to receive, transmit and evaluate local measuring signals. Also belonging, inter alia, to the methods which are considered in this case to be prior art is transmission by means of binary signals, the level of the local measuring signal being represented by the relative frequency of the occurrence of two signal states "1" and "0" of the binary signals. For this purpose, the signal to be measured is compared with the reference value at specific, mostly equidistant instants, and one of the two signal states, that is to say "1" or "0", is output, depending on the result of this comparison.
There has always been a substantial problem in this case of undertaking a reliable and central control of the reference value which is as simple as possible. This is seen to be decidedly difficult, in particular, when the aim is simultaneously to record and process a plurality of different local measuring signals.
Furthermore, an exact determination of the local measuring signal which is to be determined requires an exact stochastic uniform distribution of the reference values. For this purpose, use is frequently made in the electrical circuit arrangements according to the prior art of an ergodic or stochastic random-check generator. It is to be regarded as a serious disadvantage in this case that such extremely complicated devices can be controlled only with difficulty. Furthermore, when a random-check generator is used there is a need for a very large number of generated reference values in order to be able to assume the required uniform distribution of the reference values. This has the disadvantageous consequence, in particular, that recording the local measuring signals over a lengthy period is indispensable.
Electrical circuit arrangements known to date have these serious disadvantages in a more or less prominent fashion. An electrical circuit arrangement for transmitting and displaying physical quantities or signals, present in electric form, by means of binary pulse trains is disclosed in German Patent Specification 22 32 450. There is to be gathered from this printed publication an arrangement of at least one comparator which compares threshold values generated by at least one stochastic generator with the amplitudes of physical quantities or signals, and makes binary decisions on the basis of these comparisons for the purpose of forming the output values, these output values occurring in the form of a pulse train. Although the conversion of an analog measured value into a digital bit sequence in which the frequency of the occurrence of the signal state "1" is proportional to the analog measured value follows from this printed publication, no central and standard control of the reference value to which the analog measured value to be determined is to be referred is provided. Rather, in the case of a use of two circuit arrangements disclosed in this printed publication, and of the combination of these to form a new arrangement by means of a logic network, all that is to be realized is a binary intermediate form which is proportional to the linear mean value of the product of the two local measuring signals to be determined. This patent specification provides no possibility for the separate determination of the two local measured values independently of one another.
In addition to this not inconsiderable deficiency, the use, disclosed in this printed publication, of a stochastic generator shows up diverse problems. Thus, in the case of a simultaneous arrangement of a plurality of, or even very many circuit arrangements, it is not possible to avoid a multiplicity of expensive devices such as, for example, stochastic generators. The overall circuit becomes very expensive, difficult to grasp and complicated.